Weighing choice on Iraq: war debate follows ancient ritual. (Commentary).

You hear echoes everywhere, if you listen closely to the debate over the coming war with Iraq.

You hear it when Democratic Sen. Edward Kennedy says war must only be undertaken as a "last resort," or when Democratic Sen. Dianne Feinstein worries the U.S. lacks "a just cause" for toppling Saddam Hussein. You hear it from war supporters and critics when they debate whether the U.S. or the United Nations Security Council is the "competent authority" to approve the use of force.

What you're hearing is moral philosophy -- not a common mode of discourse among Ted Kennedy and his colleagues. The terms they use are drawn, knowingly or otherwise, from what moral philosophers and theologians call the "just-war tradition," a line of reasoning meant to determine when, why and how a civilized nation can legitimately go to war.

The current debate brings the tradition into the 21st century, with contentious results. "It just shows how deeply embedded the tradition is in our cultural memory," says George Weigel, a Catholic theologian and author.

Just-war thinking dates back at least to Cicero, who hoped to temper the imperial appetites of his fellow Romans more than 2,000 years ago by distinguishing between moral and immoral wars.

The thinking was laid out systematically by the Christian theologians Augustine and Aquinas. Since then, in the hands of secular philosophers, just-war theory has shed many of its specifically Christian trappings to become a universal way of judging the merits of armed conflict.

The Bush administration's foreign policy apparatus is honeycombed with people steeped in just-war theory. Their influence is felt in the administration's war rhetoric, such as when President Bush, in his State of the Union address, condemned Saddam's depredations: "If this is not evil, then evil has no meaning."

When and how such an evil may be confronted is the point of just-war theory. It holds that war can be justified only under certain conditions: Does the war have a "just cause," to defend innocents against an imminent threat? Is it declared and waged by a "competent authority" -- that is, a public executive responsible for maintaining order? And is force used only as the "last resort"?

To each of these questions, critics of the administration's Iraq policy say no. Weigel says a correct reading of-just-war thinking, applied to the new realities of the age of terror, yields a different answer.

Consider, he says, the concept of "just cause." "Traditionally, that is taken to mean a defense against an act of aggression that is actually underway," Weigel says. Only then, according to some readings of just-war theory, can a state respond by waging war.

"It may be more accurate to say that in the hands of certain kinds of regimes the mere possession of weapons of mass destruction constitutes an act of aggression," he says.

Weigel said many critics of Bush's Iraq policy are employing the language of "just war" while forgetting its substance. "They aren't pacifists on principle," he says. "They would never say that under no circumstances can a state use force. But they are functional pacifists. They seem incapable of conceiving a set of circumstances, short of a direct attack on our country, under which a state can use force."

Augustine stressed that under some circumstances it is immoral for the leader of a sovereign state not to wage war. Do we face such a set of circumstances now? That is a question not only for theologians and philosophers but for statesmen, and Bush is making his answer clear.

Andrew Ferguson is a columnist for Bloomberg News.